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Unread 05-07-2013, 05:51 PM   #1
Georgeninner
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98 Grand Cherokee 5.9 transmission problems?

Hello I have a 98 Grand Cherokee 5.9 Limited with 164000 miles in it and the transmission is suddenly slipping really bad. I went offroading at some dunes around where i live and everything was fine until i left. At first it felt like it was stuck on one gear and wasn't responding too good so i went ahead and stopped in the side of the road and turned off the jeep to let it cool down. Once i started it again it was driving normally except for the OD not turning on so at 60 i was almost at 3000rpms. I went ahead and drove slowly back home and right before i got there the OD turned back on by itself and my transmission was shifting perfectly fine. Once i tried moving it again I can floor it and it will accelerate extremely slow and the RPMs go up to almost 4K just to get it going to 40. It will shift into all the gears now but it feels like every gear slips and the acceleration is horrible. What could be wrong with it? My mechanic said its either a solenoid problem or the whole transmission has gone bad. What sounds like the more probable problem? The fluid level is good but it is pretty bad already could that also be the problem? Any help will be appreciated, thanks.

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Unread 05-07-2013, 06:49 PM   #2
PolkaPower
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Seems like you overheated it maybe. The OD will turn itself off when it overheats and will not come back on until it cools back down. Do you have an auxiliary transmission cooler? The 5.9 transmission is very easy to overheat since they didn't come with one from the factory. The solenoids going bad is a possibility but those usually start going bad over time, not all at once. I would drain the fluid and see what's in the pan then refill it and cross my fingers.

Did you have the OD off while in the dunes?
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Unread 05-07-2013, 10:48 PM   #3
Georgeninner
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Quote:
Originally Posted by PolkaPower View Post
Seems like you overheated it maybe. The OD will turn itself off when it overheats and will not come back on until it cools back down. Do you have an auxiliary transmission cooler? The 5.9 transmission is very easy to overheat since they didn't come with one from the factory. The solenoids going bad is a possibility but those usually start going bad over time, not all at once. I would drain the fluid and see what's in the pan then refill it and cross my fingers.

Did you have the OD off while in the dunes?
No I do not have an auxiliary cooler even though i have been thinking about getting one. What is the damage that could have been caused by overheating the transmission? And well the transmission had been feeling a little funny since i got the jeep a few months ago so maybe that was a sign of the solenoids starting to go bad. And no i did not have it off i normally don't mess with the OD at all, would it have been better to have it off at the time?
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Unread 05-10-2013, 02:40 PM   #4
BuzzZJ9er
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Quote:
Originally Posted by PolkaPower
The 5.9 transmission is very easy to overheat since they didn't come with one from the factory.
I thought the 5.9 and 96-98 5.2 had the same factory trans cooler inside the rad?
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Unread 05-10-2013, 02:46 PM   #5
Timo_90xj
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Originally Posted by BuzzZJ9er View Post
I thought the 5.9 and 96-98 5.2 had the same factory trans cooler inside the rad?
It's not an auxiliary cooler. It's a pathetic excuse for something trying to cool the tranny. I'm gettin close to too hot tranny with 4.56 gears turning 32s on my niner driving in city in hotter weather. IMO, you need to install an aux cooler if you wheel at all.
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Unread 05-10-2013, 02:53 PM   #6
BuzzZJ9er
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Quote:
Originally Posted by Timo_90xj

It's not an auxiliary cooler. It's a pathetic excuse for something trying to cool the tranny. I'm gettin close to too hot tranny with 4.56 gears turning 32s on my niner driving in city in hotter weather. IMO, you need to install an aux cooler if you wheel at all.
My niner trans actually burnt up, so when I replace it I'm going with an aux cooler for sure!

I don't get why they combined the two coolers! If one starts to run warm wont the other and double the trouble. My opinion and I could be way off...
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Unread 05-10-2013, 03:02 PM   #7
PolkaPower
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Originally Posted by BuzzZJ9er View Post
My niner trans actually burnt up, so when I replace it I'm going with an aux cooler for sure!

I don't get why they combined the two coolers! If one starts to run warm wont the other and double the trouble. My opinion and I could be way off...
You are correct. If the motor overheats it will in turn heat up the tranny and vice verse. I bypassed the radiator trans cooler and just use a large aux cooler in front of the condenser on the passenger side. It cooled my motor off a little too.

98 models had the "redesigned" trans cooler in the radiator so no ZJ's in 98 had aux coolers.
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Unread 05-10-2013, 03:11 PM   #8
BuzzZJ9er
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Quote:
Originally Posted by PolkaPower
98 models had the "redesigned" trans cooler in the radiator so no ZJ's in 98 had aux coolers.
"Redesigned" apparently means s****y! Lol
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Unread 05-10-2013, 03:20 PM   #9
PolkaPower
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"Redesigned" apparently means s****y! Lol
Yea, like they said "last year, **** it!"
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Unread 05-10-2013, 03:25 PM   #10
BuzzZJ9er
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Quote:
Originally Posted by PolkaPower

Yea, like they said "last year, **** it!"
I like your setup. Some ppl say still use stock "cooler" but if you bypass it its one less variable in the mix.
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Unread 05-10-2013, 03:28 PM   #11
PolkaPower
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Originally Posted by BuzzZJ9er View Post
I like your setup. Some ppl say still use stock "cooler" but if you bypass it its one less variable in the mix.
I have a friend that had his radiator trans cooler fail and coolant got into the transmission and killed it. That was another reason I did it. I hear that is a very rare thing but knowing someone it happened to was enough for me. You just have to make sure you get an aux cooler that will do a great job and is big enough. I put one on rated for 30,000 GVW. I had a smaller one on there before that and it just wasn't cutting the mustard.
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Unread 05-10-2013, 03:57 PM   #12
BuzzZJ9er
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Quote:
Originally Posted by PolkaPower

I have a friend that had his radiator trans cooler fail and coolant got into the transmission and killed it. That was another reason I did it. I hear that is a very rare thing but knowing someone it happened to was enough for me. You just have to make sure you get an aux cooler that will do a great job and is big enough. I put one on rated for 30,000 GVW. I had a smaller one on there before that and it just wasn't cutting the mustard.
Wow! That's a scary thought. I'm going to have to suggest my wife do this also with her 5.2. Thanks for the heads up!
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Unread 05-10-2013, 04:04 PM   #13
MurdaJs
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Originally Posted by PolkaPower View Post
I have a friend that had his radiator trans cooler fail and coolant got into the transmission and killed it. That was another reason I did it. I hear that is a very rare thing but knowing someone it happened to was enough for me.
Exact thing happened to my dad, about 750 miles from home
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Unread 05-10-2013, 09:48 PM   #14
StPaul59
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Quote:
Originally Posted by PolkaPower View Post
I have a friend that had his radiator trans cooler fail and coolant got into the transmission and killed it. That was another reason I did it. I hear that is a very rare thing but knowing someone it happened to was enough for me. You just have to make sure you get an aux cooler that will do a great job and is big enough. I put one on rated for 30,000 GVW. I had a smaller one on there before that and it just wasn't cutting the mustard.
Would the trans be ok in the winter time with the bypass? I would think you should cover the cooler when it gets cold outside at least.
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Unread 05-10-2013, 10:44 PM   #15
PolkaPower
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Originally Posted by StPaul59 View Post
Would the trans be ok in the winter time with the bypass? I would think you should cover the cooler when it gets cold outside at least.
Never had a problem this winter. Didn't block the cooler with anything either. Overdrive functioned shortly down the road so I didn't worry about it. ATF-4 works well in the cold.
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